Monazite is one of four major raw materials of rare earth industry in China. The monazite is mainly contained in beach placers of Guangdong, Guangxi and Hainan Island and mainly associated with zirconium, titanium and other minerals; and there are monazite ores inland, for example, a super-large monazite mine exists in Gangkou, Yueyang, Hunan. The monazite belongs to light rare earth ores. The existing production process is as follows: performing alkali decomposition on monazite concentrate, and extracting useful rare earth and phosphorus from material liquid, wherein the remaining solid products, i.e. monazite slag, contain about 16-28% of ThO2, 0.6-1.2% of U and 9-20% of REO, as well as the monazite, zirconite, rutile and other useful minerals, which are not decomposed. As how to make thorium with the highest content more useful has not been found out, no attention is paid to the recovery of these monazite slag, and these monazite slag become a heap of troublesome radioactive waste slag, which is not conductive to environment-friendly management and also becomes an insurmountable obstacle in survival and development of a rare earth plant taking the monazite as raw material. At present, there is about 50,000 tons of monazite slag all over China, and nearly 10,000 tons of mineral slag is produced annularly; and if the management is not regulated, the environment will be greatly harmed.
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.
It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior or to provide a useful alternative.